We study the response to predators by the rolly-polly ( Tracheolipus rathkii ).
Predators are scary and fear of them changes how animals behave. The impact of fear is a long-standing research area in ecology that, in part, tries to predict how fear of predation aalters ecosystems. Yet, it is still difficult to know when prey animals will be afraid of a predator enough for it to change their behaviour and thier role within the ecosystem. The studies that have surveyed prey for fear effects don't always find a response.
We use this wolf spider ( Gladicosa gulosa ) as a predator because they eat many of the detritivores in the old fields.
Nathalie Sommer and I have measured the response of some common decomposer species--rolly-pollies, crickets, millipedes, and earthworms--to predators. We can infer a fear response by looking for increases in breathing rate (metabolism), consumption of carbohydrates, and changes in their behavior. Previous work has shown that predators who ambush prey tend to cause a stronger fear response. There are two reasons why ambush predators cause more fear responses. First, they remain stationary and so create a dangerous area for prey in areas with desirable resources. Second, they tend to kill fewer prey, so the effect of fear is more noticable. Our preliminary results suggest that the response of the prey species also matters. Prey whose methods of escape are based on reaction time show stronger evidence for fear effects than species who defend themselves chemically or physically. Check back soon to hear how our full results turn out!
In our experiments we track the consumption of leaves using repeated images and summing up the area consumed.